performance when adding expiration date

We are currently running v0.9 of your plugin. It has worked great for a year. We will shortly update to 1.0 but we have begun having performance issues. When we edit the user to add an expiration date the page often times out and results in a white screen. Can you provide minimum memory requirements or any other cause or solution to this problem?

thanks!

https://ww.wp.xz.cn/plugins/expire-users/